Contamination of soil and groundwater by various compounds including both organic and inorganic chemicals is widespread. This contamination threatens human health, public safety, public welfare and the environment. Attempts to remediate contaminated soil and/or groundwater by a variety of means are common.
Two of the existing methods of remediation of contaminated soil and/or groundwater are chemical treatment and biological treatment. Typically, chemical treatment consists of oxidation of the contaminants via application of remedial additives such as hydrogen peroxide, Fenton's Reagent, ozone, sodium or potassium permanganate or bisulfate. Typically biological treatment consists of stimulating microorganisms that are either naturally occurring at or near the treatment location or introducing cultured microorganisms into the treatment area.
There are disadvantages to the common methods of chemical oxidation. The prior art of chemical oxidation frequently relies of the use of strong acids and metallic salts (such as ferrous sulfate) to enhance the chemical reaction. The use of these compounds can be dangerous and costly, and can cause new soil and groundwater contaminant conditions. Chemical treatment, particularly oxidation of contaminants with remedial additives, has been shown to have a detrimental effect on the abundance of microorganisms. These negative effects are primarily due to changes in pH levels and the inherent sterilizing qualities of the materials and methods used in the injections. Table 1 shows the dramatic reduction in the abundance of certain known types of microorganisms as a result of a typical chemical oxidation treatment. In this example case, iron catalyzed hydrogen peroxide was injected into wells to treat soil and groundwater contaminated with gasoline. This treatment method reduces or eliminates the beneficial remedial effect that microorganisms have on the treatment of soil and groundwater. As a result, completion of the treatment process must rely solely on the chemical process.
The prior art of chemical treatment typically relies on the use of strong oxidants so that the chemical treatment works as quickly as possible. As a result of the prior art's bias towards strong oxidants, which are also typically strong sterilizing agents, biological treatment and chemical treatment have not previously been integrated. Those of ordinary skill in the art typically hold the view that integration of oxidants and biological treatment is counter-intuitive. The subject invention offers improvements over the prior art of chemical oxidation by modification of the oxidation process so that it can be effectively integrated with biological treatment.
Biological treatment relies on soil and groundwater conditions being optimized so that naturally occurring or artificially introduced microorganisms can consume the soil and groundwater contaminants. The biological treatment process is slow because of various factors. Competition between the various known types of microorganisms present at the treatment site limits the rate of biological remediation. Large and small-scale variation in the contaminants and the biologically necessary nutrients and electron receptors can affect the efficacy of the treatment. It is a challenge in biological treatment to collocate the remedial additives with the contaminants so that biological activity occurs in the area targeted for remediation. Contaminants are also frequently adsorpted on soil grains, providing little available surface area for the microorganisms to access. Biological treatment is also limited by the temperature of the soil and groundwater with lower temperatures typically resulting is slower biological treatment. As a rule of thumb, microbial respiration rates, which are related to remediation rates, will double with each 10 degree Celsius increase in temperature. The subject invention offers improvements over the prior art of biological treatment by collocating the remedial additives with the contaminants, desorbing the contaminants from soil into groundwater, and increasing the subsurface temperature.
TABLE 1Detrimental Impact of Chemical Oxidation on MicrobialAbundance in GroundwaterPre-treatment MicrobialPost-treatment MicrobialMonitoring WellAbundanceAbundanceWell 118,000165Well 2160,00049,000Note: Units of Microbial Abundance are Colony Forming Units per milliliter (CFU/mL) as measured by heterotrophic plate count. 
It is the object of the present invention to provide an improved method for soil and/or groundwater treatment.
It is another object of the present invention to overcome the shortcomings and inefficiencies of prior art chemical treatment methods for soil and/or groundwater contamination.
It is another object of the present invention to overcome the shortcomings and inefficiencies of prior art biological treatment methods for soil and/or groundwater contamination.
It is yet another objective of the present invention to provide an improved, cost efficient soil and/ or groundwater remediation process which integrates both chemical and biological treatment.